Environmental and geological controls on the diversity and
distribution of the sauropodomorpha

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Abstract

Sauropodomorph dinosaurs were an important component of Mesozoic terrestrial ecosystems.
Their diversity and abundance fluctuated throughout the Mesozoic but whether this reflects
genuine biological changes or merely variations in our sampling of the rock record is uncertain.
A database of all sauropodomorph individuals (2335) has been compiled, including
environmental, geological, taxonomic and taphonomic data. Using a variety of sampling proxies
(including a new specimen completeness metric) and a number of analytical techniques
(residuals, rarefaction and phylogenetic diversity estimates), this work has demonstrated that
sauropodomorph diversity appears to be genuinely high in the Pliensbachian‐Callovian and
Kimmeridgian‐Tithonian, while low diversity levels are recorded for the Oxfordian and
Berriasian‐Barremian, with the J/K boundary seemingly representing a real diversity crash.
Diversity in the remaining Triassic‐Jurassic stages appears to be largely controlled by sampling
biases while Late Cretaceous diversity is difficult to elucidate and perhaps remains relatively
under‐sampled. Sea level affects diversity and abundance in the Jurassic‐Early Cretaceous, but
does not appear to be linked in the Late Cretaceous. Different clades of sauropodomorphs
potentially preferred different environments and this may have had an effect on changes in
their distribution and diversity. Titanosaurs have been demonstrated to show a preference for
inland environments compared to non‐titanosaurs, and it is possible that this led to their
success in the Cretaceous when other sauropod clades were in decline. An assessment of the
palaeolatitudinal patterns of sauropods and ornithischians reveals a distributional skew in the
Late Cretaceous, which may reflect environmental and/or dietary preferences. A study of
completeness through historical time contradicts the recent claim that the quality of
dinosaurian type material has improved from the 19th century to the present. These studies
illustrate that use of a number of techniques is imperative in any attempt to tease apart genuine
patterns from the biases of an uneven rock record.

Type:

Thesis
(Doctoral)

Title:

Environmental and geological controls on the diversity and
distribution of the sauropodomorpha